(CNN) -- Texas authorities on Sunday were searching for a convicted burglar who escaped from a medical facility by rappelling off the building using a string of bedsheets, officials said.

Joshua Duane Barnes, 21, was serving 35 years in prison for several convictions, including two escape charges.

Joshua Duane Barnes, 21, was last seen at 8:15 p.m. Saturday on the seventh floor of a Texas Department of Criminal Justice medical facility in Galveston, Texas, said TDCJ spokesman Jason Clark.

Fifteen minutes later, Barnes was gone, Clark told CNN.

Security officers noticed there was a hole in the wall and a vent had been removed.

According to Clark, Barnes busted a hole through a wall in his room and then broke through a thick window.

He apparently tied bedsheets together, rappelled down the side of the building to a roof, and then jumped to the ground, Clark said.

Barnes was serving 35 years in prison for several felony convictions, including seven burglary charges, two escape charges and an aggravated assault charge in the Texas Panhandle area, according to a TDCJ press release.